🌡️ Everyday physics

Heat always moves from warmer things toward cooler things, never the other way around, until both reach the same temperature, this is one of the most reliable patterns in all of physics. It can move in three different ways, by direct touch between objects, by flowing through moving liquid or gas, or by travelling as invisible waves through empty space, which is exactly how the sun's heat reaches Earth. A cold drink left out on a warm day always warms up, and a hot drink always cools down, heat is constantly trying to spread out evenly.

Sound is created when something vibrates, shaking back and forth fast enough to push and pull on the air around it, sending that vibration outward in waves until it reaches your ear. Your ear catches those vibrating waves and turns them into signals your brain reads as sound, a lower or higher pitch simply means the vibrations are happening more slowly or more quickly. Sound needs some kind of matter to travel through, air, water or solid material, which is exactly why there is no sound at all in the empty vacuum of space.

A ramp makes lifting something easier by trading distance for force, you push something a longer path instead of straight up, so it takes less force at any one moment, even though you end up doing the same total amount of work either way. The steeper a ramp gets, the closer it becomes to just lifting something straight up, so the easier-pushing benefit shrinks the steeper the ramp is. Engineers carefully calculate the gentlest ramp angle that still fits the available space, since a very long, gentle ramp needs far less force but far more distance to travel.

Whether something floats or sinks depends on comparing its density, how much mass is packed into its size, to the density of the liquid it is in. An object less dense than water floats, while an object more dense than water sinks, which is why a huge steel ship can float, its overall shape traps enough air to make its average density lower than water, even though solid steel itself would sink straight away. Water actually pushes upward on anything placed in it with a force called buoyancy, and an object floats exactly when that upward push matches its own downward weight.